Turn On a LED on STM32F4-discovery

Or heaven forbid, use the debugger, and have the while loop alternately drive the led high and low, and step through the code to confirm it's actually being run.

The code looks Ok.

Or heaven forbid, use the debugger, and have the while loop alternately drive the led high and low, and step through the code to confirm it's actually being run.

The code looks Ok.

Hi guys,

I launched a debug session for this code :

int main()
{
        // Enable the GPIOD Clock
        RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);

        // GPIOD Configuration
        GPIO_InitTypeDef GPIO_InitStruct;
        GPIO_InitStruct.GPIO_Pin                = GPIO_Pin_15;                  // Led 6 Blue selected
        GPIO_InitStruct.GPIO_Mode       = GPIO_Mode_AF;                 // Mod out !
        GPIO_InitStruct.GPIO_Speed      = GPIO_Speed_50MHz;     // 50 MHZ clock frequency
        GPIO_InitStruct.GPIO_OType      = GPIO_OType_PP;                // Push pull mod
        GPIO_InitStruct.GPIO_PuPd       = GPIO_PuPd_UP;                 // Pull up

        GPIO_Init(GPIOD, &GPIO_InitStruct);

        // GPIOD-PIN 15 ON
        while(1)
        {
                GPIO_SetBits(GPIOD, GPIO_Pin_15) ;
        }
}

Here is the result of debug session :

    12:         // GPIOD Configuration
    13:         GPIO_InitTypeDef GPIO_InitStruct;
0x080004E2 2101      MOVS          r1,#0x01
0x080004E4 2008      MOVS          r0,#0x08
0x080004E6 F7FFFF3D  BL.W          RCC_AHB1PeriphClockCmd (0x08000364)
    14:         GPIO_InitStruct.GPIO_Pin               = GPIO_Pin_15;                         // Led 6 Blue selected
0x080004EA F44F4080  MOV           r0,#0x4000
0x080004EE 9000      STR           r0,[sp,#0x00]
    15:         GPIO_InitStruct.GPIO_Mode       = GPIO_Mode_AF;                     // Mod out !
0x080004F0 2002      MOVS          r0,#0x02
0x080004F2 F88D0004  STRB          r0,[sp,#0x04]
    16:         GPIO_InitStruct.GPIO_Speed      = GPIO_Speed_50MHz;  // 50 MHZ clock frequency
0x080004F6 F88D0005  STRB          r0,[sp,#0x05]
    17:         GPIO_InitStruct.GPIO_OType      = GPIO_OType_PP;          // Push pull mod
0x080004FA 2000      MOVS          r0,#0x00
0x080004FC F88D0006  STRB          r0,[sp,#0x06]
    18:         GPIO_InitStruct.GPIO_PuPd       = GPIO_PuPd_UP;                     // Pull up
    19:
0x08000500 2001      MOVS          r0,#0x01
0x08000502 F88D0007  STRB          r0,[sp,#0x07]
    20:         GPIO_Init(GPIOD, &GPIO_InitStruct);
    21:
    22:         // GPIOD-PIN 15 ON
0x08000506 4669      MOV           r1,sp
0x08000508 4804      LDR           r0,[pc,#16]  ; @0x0800051C
0x0800050A F7FFFEDB  BL.W          GPIO_Init (0x080002C4)
    23:         while(1)
    24:         {
0x0800050E E004      B             0x0800051A
    25:                 GPIO_SetBits(GPIOD, GPIO_Pin_15) ;
0x08000510 F44F4180  MOV           r1,#0x4000
0x08000514 4801      LDR           r0,[pc,#4]  ; @0x0800051C
0x08000516 F7FFFF1D  BL.W          GPIO_SetBits (0x08000354)
0x0800051A E7F9      B             0x08000510
0x0800051C 0C00      DCW           0x0C00
0x0800051E 4002      DCW           0x4002
0x08000520 F04F7040  MOV           r0,#0x3000000
0x08000524 EEE10A10  VMSR           FPSCR, r0
0x08000528 4770      BX            lr
0x0800052A 0000      MOVS          r0,r0
0x0800052C 053C      DCW           0x053C
0x0800052E 0800      DCW           0x0800
0x08000530 0000      DCW           0x0000
0x08000532 2000      DCW           0x2000
0x08000534 0660      DCW           0x0660
0x08000536 0000      DCW           0x0000
0x08000538 01C4      DCW           0x01C4
0x0800053A 0800      DCW           0x0800
0x0800053C FFFFFFFF  DCD           0xFFFFFFFF
0x08000540 FFFFFFFF  DCD           0xFFFFFFFF

I wonder if my homemade base project is well configured. Maybe the uC isn't well init.

I think there is also some code before main in the start up file that will be performed
to set up the clocks. That is why I suggested that you use system viewer to look at the RCC.

Can you right click on the project so you can get to project options and the debug tab.
and the Unclick the run to main checkbox. then run debug. choose to single step into the code.

What function does the debugger go to. Does it go into a function probably called system_init.
This is where it would initialize the clock stuff. this code is before the main function in another file that is assembly code.

also can you find a function to clear the led.

Hope this helps

I launched a debug session with your advises and it runs until System init function like you said.

175:                  LDR     R0, =SystemInit
0x0800020C 4809      LDR           r0,[pc,#36]  ; @0x08000234

.

Then there is this code but i can't find a function to clear the LED :

  LDR     R0, =SystemInit
                 BLX     R0
                 LDR     R0, =__main
                 BX      R0
                 ENDP

Then with the system viewer i checked some registers. In RCC, i checked AHB1ENR and nothing is activated. In GPIOD, i checked BSRR register and nothing is activated too. It seems that clocks are not well initialized. Do you know what i must change to correct it ?

Many thanks !

One more thing that came to mind. Make sure you have the debug selected and not simulation. I think simulation might be the default mode. You should find the check box in the same place you unchecked run to main.

do some more single stepping and verify that the clock registers are really being written to.